In the conventional clutch mechanism, a release bearing for engaging and disengaging the clutch is supported by a stationary cylindrical support shaft which also supports the shaft on which the clutch disc is splined. A clutch lever or release fork is disposed substantially perpendicular to the shaft and is engaged at a rear face, at one end to one side of, for example below, the release bearing with an operation rod and is engaged at a rear face, at its other end to the other side, for example above, the release bearing with a stationary fulcrum. The lever has a pressing point, at its front face intermediate its ends, for pressing the release bearing to disengage the clutch.
When a clutch pedal (not shown) is depressed to release the clutch, the operating rod is advanced forwardly, toward the clutch, so that the clutch lever is pressed inwardly around the stationary fulcrum pushing the release bearing forwardly and the clutch is released. FIG. 4 illustrates a relationship between a clutch pedal stroke and an effective release stroke, i.e., movement of the release bearing. As illustrated therein, in a process in which the clutch pedal stroke increases, the movement of the release bearing initially increases slowly and curvedly due to loss in motion of the respective parts, and then increases substantially linearly.
When the pedal stroke increases after the clutch is substantially fully released, in section "a" in FIG. 4, the increasing ratio of the effective stroke remains the same. In the conventional clutch, there are only small spaces between a friction facing 6 at a radially outer portion of a clutch disc 5 and a flywheel 7 and between the facing 6 and a pressure plate 8 when the clutch is released. Therefore, if a driver revs up an engine during stoppage, e.g., at a traffice signal, the flywheel 7 may contact the facing 6 due to its axial oscillation as indicated by an arrow X2, FIG. 1, which causes a drag phenomenon or creep phenomenon. Such oscillation of the flywheel is caused by the crank shaft (not shown) of the engine which receives a reciprocating force from pistons of the engine. This oscillation causes the surface of the flywheel and/or a surface of the pressure plate rigidly fixed to the flywheel to intermittently contact the facing of the clutch.
Accordingly, it is an object of the invention to provide a release mechanism in which an effective stroke of the clutch lever relatively rapidly increases after a clutch pedal stroke which disengages the clutch, i.e., the effective stroke increases to a predetermined value so that a clutch can be more fully released.